Filtration modules for separating solids from liquids commonly utilize micro (MF) or ultra (UF) filtration type porous polymeric membranes having average pore sizes from about 0.005 to 10 microns. Two of the more common types of membranes include porous hollow fibers, (e.g. see JP 11-128692; JP H8-155275; JP 2951189; U.S. Pat. No. 5,248,424), and flat sheet composite membranes (e.g. see US 2008/0156730; US 2008/0164208 and WO 2007/036332). In operation, several modules are often interconnected to form a filtration assembly which is submerged within a water source (i.e. “feed” source) such as a settling pond or an activated sludge basin. Filtration occurs by creating a transmembrane pressure differential across the membrane surface. This is typically accomplished by drawing a vacuum from the permeate side of the membrane or by pressurizing the feed source. As a result of such transmembrane pressure, permeate flows through the pores of the membrane and is collected in a header which is sealed from the feed source. After prolonged use, solids from the feed accumulate upon the membrane surface and restrict or even block fluid flow. Conventionally pore blockage, concentration polarization, and fouling have been addressed by the use of aeration devices that generate gas bubbles which scour the outer surface of the membrane. Another common technique involves backwashing permeate through the membrane to dislodge and remove accumulated solids from the membrane surface.
Another type of flat sheet membrane comprises an integral extruded porous structure including capillary channels. This type of membrane sheet is distinguished from the aforementioned flat sheet composite-type structure in that it has an integral or unitary structure rather than a distinct multi-laminate construction. Examples of such membrane sheets are described in: U.S. Pat. No. 5,046,936; U.S. Pat. No. 5,089,187; U.S. Pat. No. 5,171,493; and US 2009/0011182. Such membranes may be extruded from a variety of polymer mixtures, e.g. polyether sulfone, polyvinylidene fluoride. U.S. Pat. No. 6,787,216; FR 2,616,812; JP 59-082906 and JP 11-90192 further describe the use of such membrane sheets within filtration modules. A. Grelot et al. describes the use of such membrane sheet in filtration modules which are combined to form a filtration assembly designed for MBR applications, see “A New and Appropriate Fibre Sheet Configuration for MBR Technologies,” Desalination and Water Treatment, 6, 25-32, Desalination Publications (2009).